The device used to activate the wormholes to enable sliding is an old modified Motorola cellphone, the MicroTAC. The new device acquired to slide in season 3 appears to be a common TV remote control. The device used for sliding in "Exodus" parts I and II is a modified Sega Genesis controller.
Even though the production of the show went on continuously between season 3 and season 4, it had a year hiatus from airing when it was dropped by Fox and picked up by Sci-Fi, making the airing years (1995-1997, 1998-2000). The special effects in the fourth season take a very noticeable dive in quality, as the series had just been canceled by Fox before being resurrected by the Sci-Fi Channel, which left the show with an overall lower production budget.
Jerry O'Connell (Quinn) wrote an episode treatment entitled "Narcotica", which took place on an Earth where drugs had been legalized. The story was rejected by the network for being "too dark," but later found life as a 'Sliders' comic book.